Fig. 2.

Overview of the morphology of small round viruses, known to be causative agents of gastroenteritis. (a) calicivirus, named according to the very distinct capsid morphology with 32 deep surface indentations (Greek ‘calix’, cup, goblet). (b) astrovirus with their typical, star-like capsid symmetry (Greek ‘aster’, star). (c) Norwalk virus, barely displaying any surface detail, named after the place, where the first outbreak caused by this virus was described. (a)–(c) Negative staining using 1% uranyl acetate. Magnification, ×80 000; bar, 100 nm.